1. Field of the Invention
The present invention relates to voltage regulators, and particularly to a linear voltage regulator for providing a high-power to a load mounted on a motherboard.
2. General Background
Linear voltage regulators are widely used to supply power to electronic devices, such as to a load on a motherboard of a computer. Such linear voltage regulators are available in a wide variety of configurations for many different applications.
A typical linear voltage regulator includes a resistive voltage divider, a three-terminal adjustable shunt regulator, and a regulating transistor. The resistive voltage divider receives an output voltage, and provides a voltage reference to the three-terminal adjustable shunt regulator. The three-terminal adjustable shunt regulator receives the voltage reference, and provides a controlling voltage to the regulating transistor. The regulating transistor controlled by the controlling voltage receives a system voltage, and provides the output voltage to a load.
When the output voltage suddenly becomes higher, the controlling voltage becomes lower correspondingly. Then a current through the regulating transistor reduces. Therefore the output voltage drops to a same level as before the sudden increase thereof. Contrarily, when the output voltage suddenly becomes lower, the controlling voltage becomes higher correspondingly. Then the current through the regulating transistor increases. Therefore the output voltage climbs to a same level as before the sudden decrease thereof.
However, An operating voltage of the regulating transistor is in inverse ratio to an operating current of the regulating transistor when a power of the regulating transistor is invariable. So the higher the operating voltage is, the lower the current is, when a power of the regulating transistor is invariable. Therefore the typical linear voltage regulator cannot provide a high-power to the load.
What is needed, therefore, is a linear voltage regulator which is able to provide a high-power to a load.